the vanilla game? there's not much else worth adding from it - and dont say feasts, they were fun exactly one time and that's it.
most people are fond of the mods for warband
Feasts weren't just a "one time fun" thing, they were a tool for the player AND an immersive component that brought life to the game. It was a tool because it served as a way to raise relationships with lords and court ladies, in this case, it can still be used, but instead TW made relationships useless as they serve no purpose. It was an immersive components because lords activities weren't just raising armies, they were also having a life. Marriages for example, no longer require you to participate in a feast, as Lords would have done... instead they have been turned into another *grind the game* 2 minutes activity that show a cutscene and you're good to go get castles and lose them over and over.
Again, it's not just them existing as a novelty, it's their usability and worldbuilding component what's important, same thing can be said about conspiring against other lords, and courtship that served as a way of extending the timeframe between the stages of the game (getting married in early game without a cent and no renown is ridiculous and lame).
Then you have conspiring against lords, ACTUAL renown and ACTUAL relationships, which meant that you couldnt just lead armies and lords just by killing looters and grinding influence, you had to actually make important deeds for people to trust you with their men.
Regarding mods, yeah, mods added the other 50% that made Warband good, and you can see Taleworlds just keeps adding features from them, formation focusing being the most recent, present in a lot of mods, but Taleworlds keeps forgetting the importance of diplomacy mods, and the importance of adding interesting characters (PoP, ACOK) into the game to make it feel alive for once. So yeah, you can include Warband mods to what I've said.